A few years ago my family was asked to participate in a study ofHNPCC, a genetic mutation that causes colon cancer. My dad's family is known to carry it, so some researchers who combine genetics with genealogy wanted to get info from us to find out more about how this mutation has spread. Thorough the study we found out that my dad has it (hence his colon cancer 25 years ago); I had a 50/50 chance of inheriting it, but I didn't get it (whew!).
What I found most interesting was the fact that they've traced all cases of HNPCC back to one man who came to America from Hesse, Germany in the early 1700's. All of us who have or have parents who have the HNPCC mutation are related to one another. I've seen the researcher's chart (names omitted) that shows all these thousands of people spread out all over the country, all going back to this one guy. I found that fascinating.
I hesitate to call it a "cool" story - because of the unfortunate genetic propensity to colon cancer in her family - but I think it's amazing that the researchers were able to determine exactly where that mutation first occurred, and in whom it first occurred, not to mention the relationships of all the people he passed it on to! As a family historian, though, I just think it's a shame that the descendancy chart she saw had names omitted!